1. Field of the Invention
This invention relates to a connector for connecting a connection wire to a printed circuit board and, in particular, to a circuit board connector which prevents a terminal connecting section on a printed circuit board from being damaged by expansion/contraction of the housing of the connector when this housing, into which a terminal has been inserted, expands or contracts as a result of a temperature change .
2. Description of the Related Art
Japanese Utility Model Laid-Open No. 51-151994 discloses a conventional connector for connecting a connection wire to a circuit board, which connector is shown in FIG. 9. Referring to FIG. 9, a connector B includes housing 10 and a terminal 12 inserted into the housing, the terminal 12 having a raised engagement element 12a, which is engaged with an engagement step 15a in an engagement section 15 of the housing body 10. The terminal 12 further includes a connecting section 12b. As indicated at 6 in FIG. 9, connection of the connector B to a printed circuit board 3 is effected by soldering the connecting section 12b, which extends through the circuit board, to the printed circuit board 3.
Referring to FIG. 10, which is an enlarged view of the essential part of the connector B, the housing 10 is made of resin (polypropylene or the like), whereas the terminal 12 is made of a conductive material (a metal belonging to the copper family). Thus, the housing 10 and the terminal 12 exhibit different coefficients of thermal expansion. Here, the coefficient of thermal expansion of the terminal 12 may be neglected since it is much smaller than that of the housing 10. When the housing 10 expands as a result of a sudden rise in temperature caused by a soldering bath or the like, the engagement step 15a of the engagement section 15 expands by a length d1 to be changed into an engagement step 15b as shown in the drawing. As a result of this change, the engagement element 12a of the terminal 12 is pushed upwards by the length d1. This causes the connecting section 12b of the terminal 12, which is engaged with the engagement step 15a, to be likewise raised by d1. As a result, concentration of stress occurs at the soldered section 6 joining the connecting section 12b of the terminal to the circuit board 3, thereby causing damage such as cracks or distortion, which may lead to a considerable degree of deterioration in the reliability of the electrical connection.
Thus, the above-described conventional engagement method, in which the housing and the terminal, made of materials having greatly different coefficients of thermal expansion, are simply engaged with each other, has the problem that a sudden temperature change caused by the soldering bath or the like may cause expansion or contraction of the housing, resulting in the generation of cracks or the like in the soldered section joining the terminal to the circuit board. Further, it is possible for the engaging element of the terminal to be deformed as a result of distortion, or four the terminal to be detached from the circuit board, resulting in disconnection or poor conductivity.
The present invention has been made in view of the above problems in the conventional method for engaging the housing with the terminal. It is the object of the present invention to provide a circuit board connector which improves the reliability in the electrical connection of the joint section between the circuit board and the terminal.